Most internal combustion engines comprise accessories such as power steering, an alternator and air conditioning to name a few. These accessories are typically driven by a belt. A tensioner is typically used to apply a preload to the belt in order to prevent slippage. The tensioner can be mounted to an engine mounting surface.
The engine may further comprise a start-stop system whereby the engine will shut down when the vehicle is not in motion, and when a driver command is received to proceed the engine will restart.
The start-stop function will tend to reverse loading on the belt. Hence, tensioners are available to accommodate belt load reversals. The tensioner may comprise one or more components which independently pivot in order to properly apply a required belt preload force in both belt drive directions. The tensioner may also be mounted directly to an accessory such as an alternator in order to save space in the engine bay.
Representative of the art is WO2014/100894 which discloses a tensioner for tensioning an endless drive member that is engaged with a rotary drive member on a shaft of a motive device. The tensioner includes a base that is mountable to the motive device, a ring that is rotatably supported by the base in surrounding relationship with the shaft of the motive device and which is rotatable about a ring axis, a tensioner arm pivotally mounted to the ring for pivotal movement about an arm pivot axis, and first and second tensioner pulleys. The first tensioner pulley is rotatably mounted to the tensioner arm. The tensioner arm is biased towards a first span of the endless drive member on one side of the rotary drive member. The second tensioner pulley is rotatably mounted at least indirectly to the ring and is biased towards a second span of the endless drive member on another side of the rotary drive member. The ring is rotatable in response to hub loads in the first and second tensioner pulleys that result from engagement with the first and second spans of the endless drive member.
What is needed is a rotary tensioner having a first torsion spring in a swing arm on a rotary arm, and a second torsion spring biasing a rotary ring and the rotary arm. The present invention meets this need.